Oral Contraceptive Agents

Med J Aust. 1986 Feb 17;144(4):201-5.

Abstract

PIP: The history of the development of oral contraceptives (OCs) has been a progressive reduction in dosage to what is now probably the lowest does that is compatible with the desired therapeutic effect -- to inhibit ovluation. Yet, controversy and argument continue. A table lists the OCs that are available in Australia. Many of these preparations, although having different trade names, have an identical composition. Since the withdrawal of sequential OCs from the Australian market, there are only 2 generic types. These are the progestogen only (mini) OCs, which consist of either 30 mcg of levonorgestrel or 350 mcg of norethisterone given at the same time every day; and the combined OCs, which contain an estrogen and a progestogen. In the last 12 months, some of the older high-dose OCs have been withdrawn, and it seems likely that further withdrawals will follow. Only 2 estrogens are used in the formulation of the OC, but there is a greater variety of progestogens. Ethinyl estradiol is used in most preparations. A small minority of OCs contain mestranol, the 3-methyl ether of ethinyl estradiol. Currently, there are only 4 OC agents that are available in Australia that contain mestranol and 2 of these contain the high doses of 100 mcg. Fundamentally, there are 2 types of progestogens -- those that contain, or are metabolized to, norethisterone and those that contain norgestrel or its close relative, desogestrel. With the exception of the norgestrel group and desogestrel, all other progestins, including norethisterone itself, are effective in vivo after they have been metablized to norethisterone. Mestranol is effective in humans after demethylation to ethinyl estradiol. In the norgesterel group, since d-norgestrel is inert endocrinologically, 250 mcg of levonorgestrel and 500 mcg of dl-norgestrel are equivalent. Levonorgestrel and desogestrel are of approximately equal potency. With the combined OC agents, the overwhelming mechanism of action is by the inhibition of the midcycle peak of luteinizing hormone (LH) secretion and, hence, the inhibition of ovulation. Progestogen-only OCs have additional actions such as effects on cervical and fallopian tube mucin. Minor side-effects include disturbance of the menstrual cycle, changes in weight, and changes in mood. Major side-effects relate to 4 areas -- subsequent reproduction, the cardiovascular system, other metabolic effects, and the risk of malignancy. A table presents the absolute contraindication contraindications. There is not the slightest doubt that a woman who is over 35, who smokes, and who, in addition, may be obese and has hypertension should not use OCs. Progestogen (mini) OCs have a slightly higher failure rate and a greater incidence of irregular bleeding than have combined OCs. The mini OC has little place in women who need effective hormonal contraception and good cycle control. The mini OC may have a place in a patient who finds other contraception unacceptable and in whom estrogens are contraindicated specifically.

MeSH terms

  • Body Weight / drug effects
  • Breast Neoplasms / chemically induced
  • Cholesterol, HDL / blood
  • Contraceptives, Oral* / adverse effects
  • Contraceptives, Oral* / pharmacology
  • Contraceptives, Oral, Combined / adverse effects
  • Contraceptives, Oral, Combined / pharmacology
  • Depression / chemically induced
  • Estradiol Congeners / adverse effects
  • Estradiol Congeners / pharmacology
  • Female
  • Humans
  • Hypertension / chemically induced
  • Lactation / drug effects
  • Menstruation / drug effects
  • Myocardial Infarction / mortality
  • Pregnancy
  • Progesterone Congeners / adverse effects
  • Progesterone Congeners / pharmacology
  • Reproduction / drug effects
  • Risk
  • Thromboembolism / chemically induced
  • Uterine Cervical Neoplasms / chemically induced

Substances

  • Cholesterol, HDL
  • Contraceptives, Oral
  • Contraceptives, Oral, Combined
  • Estradiol Congeners
  • Progesterone Congeners